The present invention relates to a semiconductor device manufacturing method. The present invention can be suitably used in a method of manufacturing a semiconductor device including a photolithography process using, for example, a photo mask.
In a semiconductor device manufacturing process, a photolithography process is performed, in which a semiconductor substrate is irradiated with exposure light via a photo mask (a mask) where a circuit pattern is formed and a circuit pattern is transferred onto a photoresist film (a resist film) formed on the semiconductor substrate. Also, to increase resolution by shortening the wavelength of exposure light, EUV (Extreme Ultraviolet) lithography using EUV light with a wavelength of 13.5 nm, which is far shorter than the wavelength of an argon fluoride (ArF) excimer laser (193 nm), is being developed.
EUV light is absorbed in almost all substances. Therefore, in EUV lithography, an absorber pattern is formed on a mask blank having a front surface to which a multilayer reflective film is formed, thereby configuring an EUV mask. If a defect having a very slight height on the order of a fraction of the wavelength of exposure light (such a defect is hereinafter referred to as a phase defect) occurs in this EUV mask, a transfer defect occurs in the pattern transferred to the resist film.
A method of handling a phase defect occurring in the EUV mask includes the following three processes. A first process is a process of inspecting the phase defect. A second process is a process of estimating a correction amount of an absorber pattern, etc. A third process is a process of correcting the absorber pattern according to the estimation.
In the first process, an inspection of the mask blank before the absorber pattern is formed and an inspection of the EUV mask after the absorber pattern is formed are performed. Of these inspections, as a method of inspecting a mask blank, an exposure-light (at wavelength or Actinic) defect inspecting method has been provided in which a phase defect is detected by using EUV light having the same wavelength as the wavelength for use in exposure.
Japanese Patent Application Laid-Open Publication No. 2003-114200 (Patent Document 1) describes a method using a dark field as an exposure-light defect inspecting method. Japanese Patent Application Laid-Open Publication No. 06-349715 (Patent Document 2) describes an X-ray microscopic method using a bright field as an exposure-light defect inspecting method. Also, United States Patent Application Publication No. 2004/0057107 (Patent Document 3) describes a method of concurrently using a dark field and a bright field as an exposure-light defect inspecting method, in which a phase defect is detected by using the dark field and the phase defect is identified in the bright field using a Fresnel-zone plate.
In the second process, a correction amount of the absorber pattern and so forth are estimated. Japanese Patent Application Laid-Open Publication (Translation of PCT Application) No. 2009-507251 (Patent Document 4) describes a method of determining an intensity distribution in an image plane of a projection exposure system based on AIMS (Aerial Image Measurement System).
In the third process, an absorber pattern is corrected. Japanese Patent Application Laid-Open Publication (Translation of PCT Application) No. 2002-532738 (Patent Document 5) describes a method of changing an absorber pattern on the front surface of the mask blank adjacent to the phase defect.
On the other hand, in other lithography techniques than EUV lithography, multifocal superposing exposure may be performed, in which multiple exposure is performed while changing a focal position. Japanese Patent Application Laid-Open Publication No. 63-42122 (Patent Document 6) and Japanese Patent Application Laid-Open Publication No. 2007-123897 (Patent Document 7) describe an exposure method called FLEX (Focus Latitude EXposure Method) as an exposure method of performing multiple exposure while changing a focal position. Also, Japanese Patent Application Laid-Open Publication No. 09-306829 (Patent Document 8) describes technology in a scanning exposure method of performing exposure while scanning a reticle along an in-plane direction of a substrate, in which the position of the reticle is repeatedly displaced in a minute distance range along a direction orthogonal to the in-plane direction of the substrate.